How many times have we lost data due to corrupt hard disk, pen drive or CD/DVD. Many a times have I stored data in an external drive meant to be taken over to another computer at another location, but upon reaching, I found somehow the data vanished. External hard disks are an option, but again, not fail-safe. A small 3 feet drop, and chances are that they are dead! Well, those days are gone. Now, we have multiple options of storing data online, with the advent to multiple backup services. There is a huge range of free services like Dropbox (2GB free, recommended), Sugarsync (5GB free, recommended), UbuntuOne (5GB free, recommended), ADrive (50GB free, but with advertisements and only web interface), filesanywhere (1GB free) and others.
If you need more space, there are a wide range of highly reliable storage (and cheap!) services offered by Google Storage Services and Amazon S3. Their services require you to have technical knowledge to use. For example, Amazon S3 is actually a web service, and third party tools are required to use them with Windows. For non-technical users, it is better to go for paid services of Dropbox, Sugarsync, UbuntuOne or others.
There are tools available to enable entire website backup to one of the above services. For example, this website is undergoes an automated daily backup on Dropbox and Sugarsyc (yes, multiple backups, just in case). Moreover, Amazon S3 actually offers static website hosting as well, and is not susceptible to websites going gown in heavy loads.
Also, most of these services offer data sharing features, wherein we can share data over multiple computers, or send large data from to others by exposing via URL.